The easiest would probably be .take an usb rs232 transformer .. and now you have a rs232 on your laptop
Now take a optocoupler ..wire in series with a normal led the led side of the opto Now with emitter to ground and collector to ptt circuit is complete The opto with the led should go to rts and ground . If the rig key reversed (soft is on receive, trx is keyed) Reverse connection on rts and ground of the led´s High signal on rs232 is minus 5-12V and low signal is plus 5-12 so the led should light when minus 5v are on the rts pin Maybe a small resistor in series with the leds if you have a stationary pc cause there the voltage on rs232 is 12-15v With the usb _rs232 transformer you have only +/-5V on rts .. Rs232 is current protected at 15-20mA so the led and the led in the opto will light and the opto will switch trx Cause you need only 2-3 parts everything can fit in a rs232-plug Greetz Dg9bfc Sigi ps the opto helps to protect you from groundloops so ad transformers to audio as well and you have a good setup _____ Von: digitalradio@yahoogroups.com [mailto:digitalra...@yahoogroups.com] Im Auftrag von Jonathan Gesendet: Mittwoch, 4. November 2009 22:39 An: digitalradio@yahoogroups.com Betreff: [digitalradio] Simple PTT interface circuit ISO I'm trying out a Mizuho MX-7S QRP HT with PSK31, but I need a simple circuit to key the PTT. This rig has a "Speaker" and "Mic" output, the sleeve of "MIC" being PTT. The schematic of the radio is here: http://www.flickr. <http://www.flickr.com/photos/jonathancharles/4076077872/> com/photos/jonathancharles/4076077872/ I would like to use my Jornada 720, but also have a laptot, a Lenovo Windows XP machine with USB ports, but no RS-232 port. For a beginner, I know how the audio components get to and from the rig, but how do I key the transmitter? Presumably I will use Pocketdigi or Digipan. Thanks, Jonathan KC7FYS
